Exactly 453.592 grams are equivalent to 1 pound. Depending on what is being weighed or the conversion chart being used, 453.592 is often rounded to the closest whole number of 454 grams or to 453.6 grams.
In scientific applications, grams are often used to measure mass rather than weight, which differ slightly. Weight is directly proportional to the amount of gravity a person or object is being pulled by, while mass is the same no matter where a person or object is. For instance, an object's weight in space is less than the same object's weight on Earth, but the object's mass is exactly the same in both places.